Really 20 players max on that connection, 30 is a bit too optimistic at 33 tickrate.

Please everyone do NOT use that tutorial, with all respect but... what that tutorial tells you is complete bullshit (well most of the info)
The charts are way off... there's no way you can run 30 players from 1,5mbit, you can hardly get 18 out of that.
Same goes for memory usage.. no way you use 1,5GB on 30 players.. I use 800MB on 120 players lol...

Well anyway, leave the tickrate at 33 when hosting above 10 players, 10 and below can be done at 66 tick.
sv_maxrate for 20 players:
2048*128/20 =~14000